Amplitude modulation of control signals over electrical power lines utilizing the response of tuning fork filters
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United States of America Patent
Stats
-
Nov 1, 1988
Issued Date -
N/A
app pub date -
Mar 26, 1987
filing date -
Mar 16, 1981
priority date (Note) -
Expired
status (Latency Note)
Importance
Abstract
An electrical signalling apparatus including a transmitter and receiver connected to the same electrical power distribution network wherein a signal generated by the transmitter is used to control apparatus connected to the receiver. The system uses a pair of amplitude-modulated low frequency signals as the control signals that react with the receiver to control apparatus connected thereto. The transmitter has an oscillator modulated by twin tuning forks and provides a signal for a period of, for example 10 seconds, determined by a time-delay relay. The receiver has a demodulator followed by two filters connected to integrators. As soon as the integrated signals reach a predetermined value, a control signal is transmitted to the output. This apparatus provides a communication system which is virtually insensitive to interferences on the distribution network and operates perfectly with weak signals.
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